1. Field of the Invention
The invention relates to a feeding device for low shaft furnaces, in particular for arc furnaces for melting scrap, it being possible for the furnaces to be closed by a cover connected to a gas-extraction device, and it being possible for a charging apparatus to be set down on the furnaces once the cover has been removed from the furnace shaft.
2. Discussion of the Prior Art
EP 0 385 434 B1 discloses a smelting unit with an arc furnace which contains a furnace vessel, comprising a furnace bottom and a vessel wall, and a vessel cover. A shaft-like charging-material preheater is arranged laterally on the furnace vessel, and a lifting apparatus is fastened on a displaceable portal arranged alongside the charging-material preheater. The lifting apparatus contains at least one liftable and lowerable carrying element which acts on the border of the cover. The displaceable portal is designed as a rotary portal.
DE 40 15 916 A1 discloses a smelting unit with two smelting furnaces arranged one beside the other, each furnace being assigned a shaft which is of more or less rectangular design in plan view and has a widening interior in the downward direction. The shaft can be closed by means of a cover and, in the process, can be displaced horizontally, e.g. on rails. In the open state of the shaft, feed material can be charged into the shaft by means of a charging-material container.
Furthermore, DE196 26 389 discloses an arc furnace in which, accessible from one side of the furnace vessel and screened thermally from the furnace interior, is provided an electrode-receiving space with at least one through-passage opening for the electrode, said opening being oriented toward the furnace interior. In this case, the furnace vessel may be made up of a bottom part and a top part, the top part then having the recess which forms the electrode-receiving space. The bottom termination of the convexity is provided with a base plate which has a through-passage opening for the electrode.
With the purpose of filling the charging container, in the case of the above-mentioned devices, the material-feeding elements have to be routed to above the border of the charging shaft. If use is made here of a scrap basket moved by a crane, it is necessary to provide a corresponding overall height for the crane track and the workshop. The invention has the object of providing a feeding device for low shaft furnaces, in particular for arc furnaces, which requires only a low workshop height and, while being of straightforward low-maintenance design, makes possible uniform distribution of the charge in the furnace shaft in an operationally reliable manner, with low energy losses and while utilizing to the greatest possible extent the thermal energy present.
The invention proposes a feeding device which comprises a charging apparatus which can be set down, alongside the low shaft furnace, on a bearing means and can be set down on the furnace shaft via moving apparatuses, in particular a pivoting and lifting apparatus. The charging apparatus can be set down more or less as desired during the phase in which the arc furnace is in operation with the result that the material-feeding device for the charging container may be arranged at as low a level as possible in the steelworks workshop. For the purposes of charging the low shaft furnace, the charging apparatus is lifted from the rest position and brought into its filling position, said apparatus being kept above the shaft of the low shaft furnace precisely at such an extent that the respective mouths do not come into contact but, at the same time, as few waste gases as possible pass out of the furnace shaft into the atmosphere.
In the rest position, the charging apparatus is connected to the flue-gas extracting device of the low shaft furnace and thus serves as a pre-heating station. The scrap has the hot gases flowing through it in the preheating chamber from above. This flow direction of the gas advantageously protects the scrap restraining apparatus to the greatest possible extent against thermal overload. The bearing means is designed as an afterburning chamber here.
According to the invention, the low shaft furnace and the scrap preheater are thus arranged independently of one another. Once the charging apparatus has been pivoted away from the furnace, the latter, in particular in the case of possible malfunctioning of the scrap preheater, is operated as a normal arc furnace.
The charging apparatus has a top part and a bottom part. The top part has a rectangular configuration and can be closed by moveable elements at its end which is directed toward the bearing means and or the furnace. In the closed state, the base which is formed in this way is gas-permeable and configured such that no charge falls through it. In an advantageous configuration, there are provided single-armed levers which are fastened on shafts in a pivotable manner.
For the purposes of damping the kinetic energy of the charge during filling of the charging container, there may be provided damping elements on which the tips of the pivotable levers are supported during the filling phase. In an advantageous configuration these damping elements are constructed from a spring element and a pivotable arm.
In the mouth region, the bottom part of the charging apparatus is in a form which corresponds with the top border of the shaft of the low shaft furnace. The form of the top border of the bearing means is adapted to this configuration.
In another advantageous configuration, the gas-permeable base is formed from bars which are plugged through the lateral wall of the charging container and can be pushed in or drawn out through said wall. For the purpose of damping the impact energy during filling, the free opening of the bearing means may be covered by a grid on which the bars are supported.
If the gas-permeable base comprises bars, the charging apparatus has a relatively low overall height and, with the exception of its bottom cover-like border, is of rectangular design.
The charging apparatus is lifted by a lifting apparatus from its bearing means to a height above the border of the low shaft furnace. In order to be moved into a position just above the shaft, use is made of a moving or pivoting apparatus. If a pivoting apparatus is used, an advantageous configuration makes use of a central column which contains elements for lifting and pivoting purposes.
In a further specific configuration, there is provided on the pivoting apparatus a fork-shaped element on which there are arranged at least three lifting elements, preferably hydraulic piston/cylinder units, by means of which the lifting movement is functionally separated from the pivoting movement.
A further separation of the lifting and moving functions is provided for in a configuration in which traveling mechanisms are used, to be precise, a horizontal traveling mechanism for moving the charging container back and forth between the low shaft furnace and the bearing means and a vertical traveling mechanism for raising and lowering from the low level of the bearing means to the higher level above the shaft of the low shaft furnace. Apart from during the brief phase in which the charging container is moved, both the furnace and the charging container are connected to the gas-extracting device. If a pivoting device is used, at least one gas-line section is provided at its top side, said gas-line section being routed at right angles and being capable of being brought into positions in which the low shaft furnace can be connected to the charging container or to the gas-extracting device or else in which there is no connection at all.